class cat():
    def sayWho(self):
        print("我是猫")
        pass

class dog():
    def sayWho(self):
        print("我是小狗")
        pass

class pig():
    def sayWho(self):
        print("我是小猪")
        pass

class Person():
    def sayWho(self):
        print("我是人类")
    pass

def intrudcution(who):
    for i in who:
        i.sayWho()
        pass
list1=[cat(),dog(),pig(),Person()]
intrudcution(list1)